August 3, 2004:
mortality studies mentioned in this section were temporarily
unavailable on a Dow web site. The studies are once
again available but on a different site. If problems
are encountered with any links, please inform Dioxinspin.com
Dows Dioxin Data website
contains two epidemiology studies that studied more than
35,000 male Dow employees and followed their mortality for
more than fifty years. Although the 2,000 or so Midland
plant employees exposed to dioxins were included in the
35,000 studied employees, these two studies were not dioxin
specific but, rather, compared the mortality of employees
exposed to a wide range of chemicals. Unfortunately, the
two large studies did not define the type or the extent of chemical
exposure experienced by the workers.
The first Study, GG Bond, et al, 1987
evaluated the mortality of 37,682 Dow employees that worked
for Dow at the Midland and Bay City sites from 1940 to 1982.
The second study, CJ Burns, et al, 2002
evaluated the mortality experience of 42,076 male employees
and 11,706 female employees at the same sites from 1940 to
1994. Although Burn, 2002 does state that the purpose of the
subsequent study is to follow the Midland and Bay City
workforce an additional twelve years, the study is
not really an update of the original 1940 to 1982 study.
Due to the large number of changes made in the composition
of the studied cohort, it is very difficult to compare Bond,
1987 and Burns, 2002.
The two studies are particularly important for they
demonstrate a number of ways that cohort composition and
cohort characteristics can be manipulated to affect the
mortality calculations and thus affect the findings and
conclusions of an epidemiology study.
However, before we examine the actual study, a short
comparison of Dow's PR summaries versus the actual summary presented in
one of the studies seems appropriate.
The Overview of Dow Worker Health Studies on Dows
Dioxin Data website summarized the Bond, 1987 study in
the following manner,
Cause-specific mortality was surveyed among 37,682 male
employees with three or more days of service between 1940
and 1982 at two Dow facilities. Comparisons of observed
mortality demonstrated lower mortality in the cohort from
each of the major causes of death, including total malignant
This summary about the total cohort is correct and does seem to indicate that all
is well with this group of workers. However, a much
different picture would have been given if the Overview included the
very next sentence from the original
among hourly employees was significant excess mortality in
the categories of other lymphatic tissue.... and both hourly
and salaried nonexempt employees experienced significantly
higher mortality from other and ill-defined cancers.
Its not surprising that the Overview also did not
quote other parts of the body of the Bond, 1987 report,
However, [in the case of the
hourly workforce] a significant increasing trend in
mortality from cancers of all sites combined was observed
with increasing duration of employment, and those employed
for 20 years or more experienced a significant excess
relative to those employed for fewer than five years (RR =
1.9, 95% CL = 1.04-1.35).
Bond, 1987 goes on,
This [higher hourly mortality] was principally attributable
to significantly increasing trends in mortality from cancers
of the stomach, large intestine, prostate and lung...
Cancers of the stomach, large intestine and prostate were
significantly elevated among those with 20 or more years of
Obviously, it would be a shame to ruin great PR spin by
including details about employees dying
prematurely. If this study was dioxin-specific, it would
certainly be classified as DioxinSpin. However, because
the study focused on general chemical exposure and not
dioxins, lets just call the PR summary
These two studies will be discussed in greater detail in an
attached document that can be accessed via the link shown
below. However, it is suggested that the reader also
examine both studies (even briefly) to gain a better
understanding of the type of information that is presented
in the two studies. Both Bond, 1987 and Burns, 2002
are available via the links shown below.
Several aspects of the Burns,
2002 study seem unusual and may even be significant enough
to label the study as flawed and unreliable. However,
I am not an epidemiologist and, perhaps, a reader with more
expertise can address what constitutes a "flawed' study.
Link to Commentary:
Bond, 1987 and Burns, 2002 Commentary
to Bond, 1987:
These and other Dow mortality studies are found on :